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This term is used for a really hard slap on an unpopular kid. When the perpetrator lines up his Niven Slap he usually will do stretches with his hand and arms. The victim can sometimes be left unconscious.
Wayne Rooney: Hey guys, I'm back at Man U!
Berbatov: *Niven Slaps* Yeah, that shut you up!
by Chimble Conroy October 24, 2010
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